Load at the time of a check of the appearance of a building, a vehicle, and the like, is large because the check is mainly performed by visual recognition. In order to reduce the load due to the check, failure detection based on image processing has become attractive.
As a method of the failure detection, for example, there is a technology by which an image of a check target is captured in advance and set as a sample image, alignment of an inspection target image and the sample image is performed, and the images are compared. As a technology of the alignment, for example, in “Feature-Based Image Mosaicing”, The IEICE Transactions Vol. J82-D-II No. 10, October in 1999, pp. 1581-1589, a technology is discussed by which one of a sample image and an inspection target image is aligned with the other image by extracting feature points of the sample image and the inspection target image and estimating a homography matrix used to perform coordinate conversion of corresponding feature points. In addition, similar related arts are discussed in Japanese Laid-open Patent Publication No. 2002-109518 and Japanese Laid-open Patent Publication No. 2007-248364.
However, there is a case in which an inspection target is moved for an image sensor row in which image sensors are arranged in array such as a line sensor when an image of the inspection target is captured by the image sensor row. When the inspection target is not moved at a fixed speed, a movement speed of the inspection target is different depending on a timing of imaging by the image sensor row, so that a distortion occurs in the captured image. The accuracy of the alignment is reduced by the distortion that has occurred in the image.
An object of the technology discussed herein is to accurately perform alignment of an image of an inspection target with a sample image even when the inspection target is not moved for an image sensor row at a fixed speed.